Lens grinding apparatus



March 1955 H. M- FORTE-R ET AL LENS GRINDING APPARATUS s sheets-sheet 1Filed Jan. 23, 1555 INVENTORS IamM/Mflwrkr March 8, 1955 H. M. PORTER ETAL 2,703,470

LENS GRINDING APPARATUS Y Filed Jan. 23, 1953 3 Sheets-Sheet 2 INVENTORS8, 1955 M, PORTER r A 2,703,470

LENS GRINDING APPARATUS Filed Jan. 23, 1953 5 Sheets-Sheet '5 HIIHHI INVENTORS LENS GRINDING APPARATUS I Harold M. Porter and Patrick H,Reardon, Hagerstown,

Md., assignors to The Mitchel-Tyler Company, Hagerstown, Md., acorporation of Maryland Application January 23, 1953, Serial No. 332,934

6 Claims. (CI. 51-60) This invention relates to lens grinding and moreparticula'rly to arrangements for continuously changing the position ofa blocker so that the lens blanks mounted therein are uniformlysubjected to action of the grinding head or cap.

In application Serial Number 230,883, filed June 11, 1951-, now PatentNo. 2,686,391, by Harold M. Porter and Patrick H. Reardon, there isshown an arrangement whereby a plurality of blockers are simultaneouslymoved through various paths such that the abrading effect of thegrinding composition is uniformly distributed over the surface of theseveral blockers. While that arrangeing head is of small radius andhandles only a single blocker and in which the blocker is so moved as topre sent every part of its surface for uniform grinding action. Thepresent invention provides a long wearing highly accurate grindingsystem in which the blockers are maintained spherical through longrepeated uses and in which the lenses .produced are of exceedingly highquality.

Other objectsand advantages of this invention will 'be apparent uponconsideration of several embodiments thereof in conjunction with theannexed drawings where- Figure l is a perspective view of a preferredform of grinding apparatus according to the present invention;

, Figure 2 is a fragmentary end view of the apparatus of Figure 1showing particularly the V-shaped channel for the reception and movementof the blocker;

, Figure 3 is, a view in side elevation of the apparatus of Figure 1showing the blocker channel and the mechanism for moving the same;

Figure 4 is a top plan view of the mechanism illustrated in Figure 3;

Figure 5 is a top plan view of a modified type of grinding apparatus inwhich the blocker is caused to engage successive portions of a V-groovelaid out in a square p Figure 6 is a view in section taken on the line66 of Figure 5;

Figure 7 is a plan view taken on the line 77 of Figure 6; and

Figure 8 is a view of a blocker with the lens blanks therein as theyappear after the grinding operation.

Referring now in detail to the form of the invention shown in Figures 1to 4 inclusive, it will be noted that a spherical blocker 10 is engagedby a grinding head or cap 11 which is connected to a spindle 12 drivenfrom the chuck of an ordinary drill press 13.

It is to be understood that the blocker 10 is a sphere normally made ofhard bearing steel and provided with a number of symmetrically arranged,radially extendlng, cylindrical cavities. Short cylindrical lens blanksare cemented in these cavities with one end of the blank projecting fromthe spherical wall. This end of the blank is ground away and intoconformity with the surface of the sphere. After grinding, the cementholdlng United States Patent 2,703,470 Patented- Mar. 8,.1

2 the lens blanks is dissolved and the Plano-convex" lenses which havebeen produced are removed;

In order that the blocker 10 will be moved continuously to present everdifferent surfaces tothe grinding cap 11 in order that the lens blankswithin the blocker will be uniformly ground, the blocker is supported bya v-trough 14 having relatively movable walls. This trough and theassociated apparatus is mounted" upon the work table of the drill press13 by any con enient means, not shown.

The trough 14 is defined by supportingplates 1 5 and 16 which areconnected at one edge to ro'ds 17and518 respectively. The rods 17 and18fare mounted for reciprocation and to that end are, connected tocrosshe'ads 21 and 22 at one end and are slotted at the otherj'endtocoact with guide pins 23' and 24. The rod 17 is hired to crosshead 21 byscrews 25 and the rod 18. is similarly fixed to the crosshead 22. Thecrosshead 21 lJJlPElISIhfi movement to rod 17 and, to this end,xit ismounted, to reciprocate on shafts 26 and 27. The crosshead 22 isslmilarly arranged to reciprocate on shafts 28" and 29. The shafts 26,27, 28 and 29 are mounted in and'extend between blocks 30 and 31 andthose blocks are supported from a plate 32 which is in turn supportedfrom a plate 33 by short blocks 34. A plate 35 also rests on plates 33and receives the threaded ends of the guide pins 23 and 24. The plate 35has a generally V-shaped cut 'out {herein symmetrically arranged aboutits vertical center Keyed toshafts 36 and 37 which are journaled in theplates 32 and 33, are two sheaves 38 and 39. The upper end of shaft 36has a pitman 40 extending therefrom and the upper end of shaft 37 has alike pitman 41. At the radially outer end of the pitman 40 there is ave'rtically extending, pin 42 which engages in along slot-43 extendinglongitudinally across the entire lower surface of the crosshead 21. Asimilar arrangement exists between the pitman 41 and a like groove inthe lower surface of the cross head 22.

An electric drive motor-gear box combination 44 is mounted on the plate32 by bolts 45 and the drive shaft of this combination has attachedthereto asheave 46 which is connected by a V-b'elt 47 to the sheaves'38and :9, as can best be understood by reference to Figure It is nowapparent that when the motor is operated the sheave 46, throughthe belt47, will rotate sheaves 38.a-nd 39. Since sheaves 38 and 39 are keyed tothe shaftslon which they are mounted and since the 'pitma'ns 40 -a'nd-41 are also keyed to the respective shafts 36 and 37, it is apparentthat thepitmans will rotate at a speeddetermined by the speed of thedrive sheave 46- d the rela tion of its diameter to the diameter of thedriven sheaves 38 and 39. In theform of the invention illustrated in thedrawings sheave 38 is larger than sheave 46. Hence the shaft 36 willrotate at a lower speed than the shaft of the motor-gear box combination44. On the other hand, sheave 39 is about the same diameter as sheave 46so that shaft 37 will rotate at about the same. speed as the driveshaft. Since the pitmans 40 andv 41 are connected to the respectiveshafts 36 and 37, they will rotate at a speed equal to the speed of theshafts on which they are mounted. This rotating movement-is imparted tothe crossheads 21 and 22, respectively, which receiprocate on the rods26, 27, 28 and 29. Since the rods 17 and 18, which carry the components15 and '16 of the blocker trough assembly, are connected to ;thecrossh'eads, it will be seen that components 15 and16 are continuouslyreciprocating at different speeds. Sometimes they are moving in thesamedirection and other times one is moving in a-direction opposite tothe other. In anycase, however, their effect on the blocker 10.is toshift continuously its position to present all portions of-its surfaceuniformly to the grinding head 11.

Ordinary lens grinding compounds of the type described in applicationNo. 230,883, now Patent No. 2,686,391,

It is to be understood that the drill press is modified by the removalof the spindle return spring so that the only weight is the ordinaryspindle weight bearing on the blocker through the cap 11. In view of thepresence ofrthe grinding composition and in view of the lining of theV-trough with rubber, the cap 11 does not drive the blocker but rotatesrelative to it to perform the grinding operation. The V-trough assembly,comprised of elements 15 and 16, is lined with a soft rubber liner 49,clearly indicated in Figures 2 and 4. This soft rubber liner, asmentioned above, prevents the rotation of blocker by action of the cap11. On the other hand, the grinding compound and the rubber 49 cause atight frictional engagement between the blocker 10 and the components ofthe V-groove so that the relative shifting of the elements and 16continuously causes the presentation of a different surface of theblocker to the grinding cap 11. This results in the grinding of goodplanoconvex lenses, the blanks for which have the appearance illustratedin Figure 8 at the end of the grinding operation.

The end plate of the frame assembly is provided with a V-cutout so thata removable trough may be inserted under the moving components 15 and 16to catch grinding compound that may fall down through the space betweenthem.

It can be seen that the foregoing apparatus is designed primarily tosecure uniform presentation of all parts of the surface of a blocker tothe grinding head. The apparatus shown in Figures 5, 6 and 7 is alsodesigned with that end in mind. Again, the blocker is ground by a capconnected to the spindle of the drill press and the illustratedapparatus is intended to be set or fastened to the drill press table inorder to move the blocker at andom to distribute the grinding effectover its surace.

In the form of the invention shown in Figures 5, 6 and 7, a V-grooveassembly in the form of a square path is located in a box 50. TheV-grooves are defined by suitably supported soft rubber 51 and the boxitself is provided with four corner legs 52 and a center leg 53. Thecorner legs rest upon a flat, square table 54 while the center leg isslightly short of the table surface and coacts with an operating arm 55which extends out from a shaft 56 journaled in the table 54 and providedat its lower end (below the table) with a sheave 57 connected by aV-belt 58 to a sheave 59. The sheave 59 is connected to the drive shaft60 of the gear box 61, which in turn is connected to a drive motor 62.

From the material just described it is apparent that operation of themotor will cause the arm 55 to rotate (anti-clockwise as viewed inFigure 7) and that such rotation will be imparted through the leg 53 tothe box 50. The movement of the box 50 is not, however, a

random movement but a guided one and to this end the table 54 isprovided with a marginal flange 63 and corner right angle members 64defining between them spaces 65 substantially equal to the width of abox leg. The flange 63 and the right angle members 64 are of equalheight and both are shorter than the legs 52.

It is now apparent that as the arm 55 rotates the box 50 is caused tomove from the starting position of Figure 5 to the lower left corner ofthis figure. It then moves across to the lower right corner of thatfigure, then up to the upper right corner of that figure through theleft corner and back to the starting position. These movements arecontrolled by the angle members 64, the length of which is so adjustedthat the length of one of them, plus the distance between an adjacentpair of them, is less than the distance between two legs of the box byan amount equal to the width of a box leg. All of this is quite apparentfrom Figure 7 where the movements of the box 50 are depicted.

The driving arm 55 is notched at 66 to prevent a dead center conditionwhen the box is in one of the corners of the square supporting table 54.

In view of the fact that the spindle of the drill press, and hence theblocker, is held bodily stationary, the movements of the box 50 impartto the blocker various rolling movements on continuously changinginternal axes and these movements evenly distribute the abrading effeetof the grinding composition. The grinding composi tion is put by handinto the groove 51 and replenished as necessary.

Since even a small amount of movement of the grinding head when theblocker is not being rolled will cause perceptible uneven grinding, asolenoid brake is associated with the drill press spindle in such a waythat when motors 44 or 62 are shut 01f the drill press spindle motor isalso shut off and the brake is applied instantly to stop the drill pressspindle. This arrangement is diagrammatically shown in Figure 1 at 67.

What is claimed is:

1. Lens grinding apparatus comprising a grinding cap having a cavityinternally complementary to a portion of the surface of a sphere, aspherical blocker partially encased in said cavity and held bodilystationary thereby, sloping elements defining a V-groove positioned toact on the projecting remainder of said blocker, means to move saidsloping elements past said blocker at different speeds to rotate theblocker on continuously shifting internal axes, and means to rotate saidcap to bring about a grinding action.

2. Lens grinding apparatus comprising a grinding cap having a cavityinternally complementary to a portion of the surface of a sphere, aspherical blocker partially encased in said cavity and held bodilystationary thereby, sloping elements defining a V-groove disposed in asquare path intersecting the projecting remainder of said blocker, meansto move said groove defining elements in a square path to bringsuccessive portions of the groove into contact with the blocker, andmeans to rotate the cap to bring about a grinding action.

3. Lens grinding apparatus comprising a grinding cap having a cavityinternally complementary to a portion of the surface of a sphere, aspherical blocker partially encased in said cavity and held bodilystationary thereby, sloping means defining a V-groove in contact withthe projecting remainder of said blocker, means to move the slopingmeans defining said V-groove at mutually difierent speeds in areciprocal path, and means to rotate said cap to bring about a grindingaction.

4. Lens grinding apparatus comprising a grinding cap having a cavityfacing downwardly and being complementary to a portion of the surface ofa sphere, means to rotate said grinding cap about a vertical axis, aspherical blocker having its upper portion encased in said cavity andheld bodily stationary thereby, means defining a supporting V-groovebelow said cap and in contact with the projecting remainder of saidblocker, said V-groove defining means including two blocker contactingsurfaces, means mounting said surfaces for independent reciprocation andcommon means to reciprocate the two surfaces at difierent speeds.

5. Lens grinding apparatus as claimed in claim 5 in which the means toreciprocate the said two surface mounting means at diiferent speedscomprises a pitman connected to each surface mounting means, each pitmanbeing mounted on a rotatable shaft, a motor, and transmission meansbetween said motor and said pitman shafts for driving said pitman shaftsat different speeds from the said motor.

6. Lens grinding apparatus comprising a grinding cap having a cavityinternally complementary to a portion of the surface of a sphere, meansto rotate said cap, the cavity of said cap being adapted partially toencase and to hold bodily stationary a spherical blocker, means defininga V groove positioned to act on the projecting remainder of the blocker,and means to move said V groove defining means in a path including atleast two opposite directions both in a plane normal to the axis ofrotation of said cap.

References Cited in the file of this patent UNITED STATES PATENTS537,971 Fuller Apr. 23, 1895 1,588,435 Adams June 15, 1926 FOREIGNPATENTS 612,828 Great Britain Nov. 18, 1948

